1. Field of the Invention
This invention relates to an ink jet recording head, and more particularly to a method for producing an ink jet recording head for the generation of small droplets of ink to be used for ink jet recording system.
Ink jet recording heads for ink jet recording systems are generally provided with minute ink discharging outlets (orifices), ink pathways and an ink discharging pressure generation portion provided on a part of the ink pathway.
2. Description of the Prior Art
In the prior art, as the method for preparing ink jet recording heads, there is known, for example, the method in which minute grooves are formed on a plate of glass or metal by cutting or etching and then the plate having formed grooves is bonded with an appropriate plate to form ink pathways.
However, in the head prepared by such a method of the prior art, there may occur excessive coarsening of the internal walls of the ink pathways worked by cutting or distortions due to the difference in etching degree, whereby ink pathways with good precision can hardly be obtained and the ink jet recording heads after preparation are liable to give ink discharging characteristics which are scattered. Also, during cutting working, chipping or cracking of the plate is liable to occur to give a disadvantageously poor yield of production. And, when etching working is applied, it involves a large number of production steps to bring about a disadvantageous increase of cost. Further, as the drawback common in the preparation methods of the prior art as mentioned above, during lamination of an engraved plate having formed ink pathway grooves and a lid plate having formed driving elements such as piezoelectric elements, heat generating elements for generating energies acting on ink, it is difficult to effect registration therebetween with good precision, thus failing to afford bulk production.
As a new method for producing ink jet recording heads which can overcome these drawbacks, there is proposed the method for production of ink jet heads in which ink pathway walls comprising a cured film of a photosensitive resin are formed on a substrate provided with ink discharging pressure generating elements and thereafter covering are provided over said ink pathways, as disclosed in Japanese Patent Laid-open Publication No. 43876/1982.
The ink jet recording head manufactured with the cured film of a photosensitive resin is excellent in that it overcomes the drawbacks in the ink jet recording head of the prior art, namely poor precision of the finished ink pathways, complicated production steps and low production yield. However, due to the bonding strength, which is not so great, between the substrate having ink discharging pressure generating elements provided thereon and the ink pathway walls comprising a cured film of a photosensitive resin, when a photosensitive resin film is employed as the covering over said ink pathway walls, the covering made of the photosensitive resin is shrunk by curing, whereby the ink pathway walls are drawn toward the direction of shrinkage of the covering until they are peeled off from the substrate. Even when the bonding strength between the ink pathway walls and the substrate may be sufficient, there is the drawback that the ink pathway walls are drawn toward the shrinking direction of the covering to give no ink pathway of the desired shape.
Further, when an adhesive of a type curable at normal temperature, a thermosetting type or a photocurable type may be employed for provision of the ink pathway walls, not only does the shrinkage of the adhesive occur similarly as described above, but also the adhesive may flow into the ink pathways to clog the ink pathways, whereby the production yield is markedly lowered.